@@ -36,7 +36,7 @@ export async function log(context, settings) {
     func = settings.reporter
   }
 
-  let diagnostics = func(
+  let diagnostics = await func(
     context.files.filter(
       (file) => file.data.unifiedEngineGiven && !file.data.unifiedEngineIgnored
     ),
 
@@ -17,7 +17,7 @@
  * @callback VFileReporter
  * @param {Array<VFile>} files
  * @param {VFileReporterOptions} options
- * @returns {string}
+ * @returns {string | Promise<string>}
  *
  * @typedef Settings
  * @property {Options['processor']} processor
 
@@ -18,6 +18,9 @@ const windows = process.platform === 'win32'
 const cross = windows ? '×' : '✖'
 const danger = windows ? '‼' : '⚠'
 
+/** @type {import('unified-engine').VFileReporter} */
+const vfileReporterPrettyAsync = async (files) => vfileReporterPretty(files)
+
 // See: <https://github.com/sindresorhus/eslint-formatter-pretty/blob/159b30a/index.js#L90-L93>.
 const original = process.env.CI
 
@@ -169,6 +172,29 @@ test('reporting', async () => {
     )
   })
 
+  await new Promise((resolve) => {
+    const stderr = spy()
+
+    engine(
+      {
+        processor: noop(),
+        cwd: new URL('two-files/', fixtures),
+        streamError: stderr.stream,
+        files: ['.'],
+        extensions: ['txt'],
+        reporter: vfileReporterPrettyAsync
+      },
+      (error, code) => {
+        assert.deepEqual(
+          [error, code, stripAnsi(stderr())],
+          [null, 0, ''],
+          'should support async reporters'
+        )
+        resolve(undefined)
+      }
+    )
+  })
+
   await new Promise((resolve) => {
     const stderr = spy()
     const cwd = new URL('two-files/', fixtures)
Original file line number	Diff line number	Diff line change
`@@ -36,7 +36,7 @@ export async function log(context, settings) {`
`36`	`36`	`func = settings.reporter`
`37`	`37`	`}`
`38`	`38`
`39`		`- let diagnostics = func(`
	`39`	`+ let diagnostics = await func(`
`40`	`40`	`context.files.filter(`
`41`	`41`	`(file) => file.data.unifiedEngineGiven && !file.data.unifiedEngineIgnored`
`42`	`42`	`),`
Original file line number	Diff line number	Diff line change
`@@ -17,7 +17,7 @@`
`17`	`17`	`* @callback VFileReporter`
`18`	`18`	`* @param {Array<VFile>} files`
`19`	`19`	`* @param {VFileReporterOptions} options`
`20`		`- * @returns {string}`
	`20`	`+ * @returns {string \| Promise<string>}`
`21`	`21`	`*`
`22`	`22`	`* @typedef Settings`
`23`	`23`	`* @property {Options['processor']} processor`